The present invention relates to a recording-medium mis-recording preventing mechanism. Specifically, it relates to a recording-medium mis-recording preventing mechanism which is mounted on a recording unit such as a video tape deck, a cassette tape deck, a floppy disk drive, or the like, for judging whether it is possible or not to record images, sounds, etc. on a recording video tape, a recording cassette tape, a floppy disk, etc.
Any recording medium such as a video tape, a cassette tape, or a floppy disk is provided with a detection hole and a removable judgement claw for closing the detection hole in order to prevent images, sounds, etc. from being recorded in the recording medium by mistake. The judgement claw is removed by bending in video tapes or cassette tapes, while the judgement claw is removed by sliding in floppy disks.
On the other hand, a recording device such as a recordable video tape deck, a recordable cassette tape deck, or a floppy disk is provided with a recording-medium mis-recording preventing mechanism for detecting whether a judgement claw of a recording medium loaded therein has been removed or not, and judging whether it is possible to record on the recording medium or not.
FIG. 4 is a schematic perspective view of a prior art recording-medium mis-recording preventing mechanism mounted on a video tape deck, viewed from the upper surface side of a deck body. For the sake of simplification, the deck body is not shown.
This recording-medium mis-recording preventing mechanism has a push switch 200 for detecting whether recording can be carried out or not, and an arm portion 500 constituted by a first arm member 510 and a second arm member 520.
The first arm member 510 has an approximate L-shape in plan view and pivotally supported at a pivot portion 511 by means of a support shaft (not shown) provided on the deck body. A falling preventing bolt (not shown) is provided on the lower side of this support shaft so that the first arm member 510 can rotate around the support shaft. Flat blade portions 512 and 513 are provided on the both sides of the pivot portion 511, respectively. A level difference just equal to the thickness of the second arm member 520 is provided between these two blade portions 512 and 513. The blade portion 513 is set to be lower in height than the blade portion 512.
At the front end of the blade portion 512, a detection portion 514 is formed so as to project toward the upper side of the deck body. A protrusion 515 for detecting the existence of a judgement claw of a video tape is formed at the front end of this detection portion 514. In addition, at the front end of the blade portion 513, a support shaft 516 for pivotally supporting the second arm member 520 is provided so as to extend toward the upper side of the deck body.
The second arm member 520 is formed so as to have an approximately L-shape in plan view and pivotally supported with a pivot portion 524 which is fitted onto the support shaft 516 provided on the first arm member 510. In addition, a support portion 521 and a push portion 522 are provided on the both sides of the pivot portion 524, respectively. The support portion 521 is disposed between the two blade portions 512 and 513 of the first arm member 510, and the support portion 521 is designed to be supported on the upper surface of the blade portion 513 so that the second arm member 520 is difficult to be detached from the support shaft 516.
A switch surface 523 for pushing a switch pin 210 of the push switch 200 provided in the deck body is formed at the front end of the push portion 522. This push switch 200 constitutes a portion of a circuit taking charge of recording, so that a recording medium is not recordable when the push switch 200 is turned off, and the recording medium can be held to be recordable when the push switch 200 is turned on.
A spring 540 is laid between the blade portion 513 of the first arm member 510 and a spring fixation portion 220 of the deck body. The spring 540 urges the arm portion 500 away from the push switch 200 (in the direction of the arrow A in FIG. 4).
A spring 530 is laid between the blade portion 513 of the first arm member 510 and the push portion 522. The spring 530 urges the push portion 522 to move forward toward the push switch 200 (in the direction of the arrow B in FIG. 4).
Then, the restoration force of the spring 530 between the blade portion 513 and the spring fixation portion 220 is set stronger than the restoration force of the spring 540 between the blade portion 512 and the push portion 522. Therefore, since the protrusion 515 enters a detection hole when no video tape is set in the deck body, the push switch 200 is not turned on though the push portion 520 is pulled toward the push switch 200 by the spring 530. Accordingly, recording is impossible.
When a video tape is set with its judgement claw not removed, the judgment claw abuts against the protrusion 515 of the detection portion 514 so that the first arm member 510 is pushed out in the counter direction of the arrow A in FIG. 4. Then, the second arm member 520 also rotates toward the push switch 200 (in the direction of the arrow B in FIG. 4) together with the first arm member so that the switch surface 523 of the push portion 522 abuts against the switch pin 210 of the push switch 200. That is, since the restoration force of the spring 530 is stronger than the restoration force of the spring 54, the rotation force of the arm portion 500 is strong enough to overcome the resistance force of the switch pin 210, so that the push portion 522 turns the push switch 200 on.
Usually, the push switch 200 is of standardize products. However, the force pushing the push pin 210 generated by the judgement claw of the video tape is sometimes too much strong, and the push switch 200 may be broken by such a strong force. Therefore, it is necessary to soften the shock in order to prevent from hitting the push pin 210 by the switch surface 523 with the strong force.
In this example, since the push portion 522 is urged toward the push switch 200 by the spring 530, the shock when the judgement claw of the video tape abuts against the protrusion 515 of the detection portion 514 is softened by the counter restoration force of the spring 530.
In addition, when the video tape is extracted, the first arm member 510 is pulled in the direction of the arrow A in FIG. 4 by the restoration force of the spring 540 to return to its initial position. At the same time, the switch surface 523 is separated from the switch pin 210 so that the push switch 200 is turned off and the push portion 522 is also returned to its initial position by the spring 530.
Not to say, when a video tape is inserted with its judgement claw being removed, the protrusion 515 of the first arm member 510 is inserted into the detection hole of the video tape, so that the first arm member 510 is not pushed out, and hence the push switch 200 is not turned on. Accordingly, the video tape is not made recordable, so that it is possible to prevent recording on the video tape by mistake.
However, in this recording-medium mis-recording preventing mechanism, at least four constituent parts, that is, the first arm member 510, the second arm member 520 and the two springs 530 and 540 were required. As a result, the manufacturing cost increased, and assembling those constituent parts was troublesome.
In addition, it is also possible to omit the spring 540 provided between the blade portion 513 and the second arm member 520 if the first arm member 510 and the second arm member 520 are integrated. But if the members 510 and 520 are integrated simply, a shock generated between the judgement claw and the first arm member 510 at the time of loading the video tape is conducted directly to the push switch 200 without being reduced which adversely affects the durability of the push switch 200.